Fibrous sheet material for the electrolytic formation of an azo dyestuff thereon



Patented Apr. 27, 1948 FIBROUS SHEET MATERIAL FOR THE ELEC- TROLYTICFORMATION OF AN AZO DYE- STUFF THEREON Myer Solomon, deceased,'late ofWestmont, N. J

by Nellie W. Solomon, administratrix, Princeton, N. J., assignor toRadio Corporation of J America, a corporation of Delaware No Drawing.

8 Claims.

This invention relates to the art of electrolytic dye production andmore particularly, to an article of manufacture involving a fibroussheet material for the electrolytic formation of azo dyestuffs thereon.In a preferred adaptation, it includes the production of dyes of theaforementioned type in connection with the art of facsimile recording.The fundamentals of the present disclosure are set forth in thecopending application Serial No. 178,743, now U. S. 1?. 2,306,471, ofwhich earlier application the present application is acontinuation-impart.

Various types of facsimile receivers are used at the present time, andin substantially all of them pictures, printed matter, or othercharacters are produced on a recording sheet of paper in response tovariations in electrical current which are received from the transmitterstation. In one type the reproduction of the character or indicia isthrough the use of carbon paper and the transfer of the carbon to therecord paper is accomplished by means of an electromagneticallycontrolled printer bar. In such a device the recording paper and carbonpaper are placed in the facsimile receiver and are moved forward atrates which are necessarily slow Joecause of mechanical inertialimitations, while line increments of the material being received arereproduced through the application of varying degrees of pressure to theprinter bar, in order that varying amounts of the carbon will betransferred from the carbon paper to the recordin paper. Such a devicefor facsimile recording is shown in the patent to Charles J. Young,Reissue #20,152, October 27, 1936.

In another type, a light sensitive recording paper is used and theamount of light permitted to strike the paper is controlled inaccordance with the electrical variations transmitted by the facsimiletransmitting device. In this type some developing or fixing processgenerally follows.

In still another type a stream of hot air is directed against a heatresponsive recording paper, the intensity of the heat or the amount ofhot air being controlled in response to the energy transmitted by thefacsimile transmitting device. Another type uses a jet of ink or somecolored Application December 23, 1942, Serial No. 469,958

pictures, is somewhat difiicult, since, for instance,

in the carbon paper method, the transfer-of the carbon to the recordingpaper is somewhat critical in response to the pressure applied to theprinter bar. Furthermore, the use of hotair or ink jets is not entirelysatisfactory since such systems are diflicult to control and to maintainin proper operation.

The present invention may be generally characterized as directed to dyeformation, in which electrolytic action plays an essential part, and isparticularly applicable to electrolytic diazotization and coupling.

It is an object of the invention to overcome the difficulties andlimitations of the prior art procedures noted hereinabove.

It is an additional object of the invention to electrolytically produceazo dyes, involving elements of novelty as to composition of matter,article of manufacture, and details of procedure.

It is another object of the present invention to obtain diazoniumcompounds by the action of an electric current on mixtures or solutionscontaining diazotizable amines and nitrites.

It is a further object to provide mixtures or solutions containingdiazotizable amines and nitrites which are adapted to electrolyticallyreact for the purpose of producing diazonium com-'- pounds.

Another object of the invention is to provide solutions or, wherefeasible, mixtures, of appropriate reagents comprising a diazotizableamine and an ionizable nitrite which are adapted for electrolyticreaction to produce a diazonium compound, and to form azo dyes from suchcliazonium compound by reaction with a coupling reagent present in saidmixture or solution.

Another object of the invention is a novel supporting material orcarrier containing dye forming chemical reagents which will reactsuitably when subjected to electrolytic treatment.

An added object of the invention is a supporting material or carriertreated with azo dye forming chemical reagents which will react suitablywhen subjected to electrolytic treatment, said carrier as a result ofits chemical treatment being electrolytically conductive.

A further object is a supporting material or carrier impregnated withreagents adapted for azo dye formation when subjected to an electriccurrent, and substantially inert to dye formation in the absence of theeiiectengendered by the electrolytic action.

A still further object of the invention is to provide a supportingsurface or carrier which is sat urated or impregnated with adiazotizable amine and an ionizable nitrite, which is advantageouslyadapted for production in situ of -a rliazoniurn compound when subjectedto an electric current.

An important object of the invention 1811;'1910- vide articles ofmanufacture adapted for facsimile recording in the form of a carrier orsupporting material treated with appropriate chemical reagents forforming a dye electrolytically when subjected to an electric current,said dye formation corresponding with electric impulses emanating from.a transmitting source, for example, irorn a scanning station.

An additional object of the invention is to provide .a supportingsurface saturatecl or impregnated with .a diazctizable amine, anionizable nitrite, a coupling reagent, an electrolyte, and otherpredetermined perfecting ingredients, s supporting surface being thereby.adapted for electrolytic facsimile recording through .azo dyeformation;

Other objects, features and advantages of the invention. willbe apparentfrom the followin detailed description.

the :plesenfi invention, it is proposed to produce the picture ofprinted :matter on the recording paper in the form of an azo dye, theamount of such dye deposited being a function of the amount of currentcaused to ilow through the recording paper. When the image :is thusformed, .ior example, by .applican-ts electrolytic azo dye formation,ithe pressure of the printer bar can be maintained constant and theamount of current which is passed through increments of the :papersimply varied in accordance with the light and dark portions present onthe picture or printed matter being scanned at the facsimiletransmitter. When dyes are so formed by electrolytic action, the varying:half tone shades may be produced by merely regulating :the amount :ofthe current which is caused to ifiow through the recording paper. 1

The electrolytic diazotization method conte plated herein can .be viewedas deriving from a general concept that mixtures of .a diazotizableamine, for example, .a suitable primary aromatic amine, and an ionizablenitrite, such as a metal nitrite or the like, are stable in mildaikaline solu tion, the amino group being un-ionized and .the nitriteion "having .a negative electric charge, "whereby diazotization issubstantially precluded and no formation .of diazoniumsalt takes place.Diazotization of these compounds may be efiected in't he presence of asuitable concentration of hydrogen ions, usually accomplished by supply-:ing an appropriate quantity .of .acid. "In the present invention, theprovision of a suitable hydrogen ion concentration is brought about bythe action of the electric current at the anode in an electrolytic cell,thus causing practically immediate diazotization or diazonium-ionformation in the region of the anode, but not before the reagents aresubjected to the electrolytic action in the effective zone of the anode.Stated in another fashion, any premature electrolytic diazotization toproduce diazonium compounds in accordance with the present invention, isprecluded by maintaining such conditions in the solutions of the .aminocompound and nitrite reagent that there is no material interreactionuntil such time as the current is passed through it; as above indieated,this control depends upon the fact that the diazotization reaction willonly take place in an acid medium, and this acid medium is madeavailable only 'in proximity to the anode. The main body of the-solutionremains fundamentally alkaline or non-acid in character.

Where couplin compounds are present in the reacting mixture, :or areadded after diazotization occurs, azo dyes are formed under conditionsappropriate to the reaction of the coupling reagent with the diazoniumcompound. Thus, where mixtures containing amines, nitrites, and couplingcompounds are subjected to electrolytic diazotization, and the couplingcompound is of the acid reacting type, coupling willoccur-substantial-ly spontaneously within an extremely brief intervalafter passage f the current which results in .the provision of an acidzone adjacent theanode.

While an acldzone is -.created and prevails adiacent the anode,-the1zone adjacent the cathode tends itcjncrease alkalinity as aresultof the current passing through the cell existing between the electrodes.-".Ehesolution as a whole is theretore preponderantly alkaline, despitethe presence of hydrogen ions produced in the anode-zone and subsequentionic migration tends to re-establish the original conditions after theelectrolysis, Accordingly, where the coupling reagent is or the typewhich reacts in an alkaline medium, the general alkalinity :of thesolution will cause the diazoni-um salt produced adjacent to the anodeto couple with the alkaline coupling reagent at any point removed fromthe anode to form the predetermined :dye product. Coupling compoundsthat react in alkaline solution frequently yield better results, whereacid coupling compounds are not suificiently reactive for the couplingto be completed before the original alkalinity is restored.

Where the compound is of the type which will couple in an alkalinemedium, there mayof course be a slightly longer time element involved toattain the aze-dye formation. This time interval is usually of the orderof less than a minute after the paissageof the-current whichcausesdiazotization. Therefore, while alkaline coupling may require asomewhat longer time interval than that necessitated by reagents whichcouple in an acid medium, alkaline coupling may, nevertheless, beappropriately classified as spontaneous, similarly to the case :of thecoupling in an acid medium.

Various regulations of the procedure obviously may be resorted to sothatboth acid coupling and alkali-necoupling may occur during the course of--formation of :a given azo dye. In general, the appropriate selectioncan be more or less guided, without limitation thereto, by consideringacid coupling as the reaction where a diazonium compound attaches itselfto the ring of the coupling Lcompound, replacing the active hydrogenwhich becomes a hydrogen ion and alkaline coupling as the reaction wherethe diazonium compound attaches to the ring of the coupling compoundwith the displacement of hydrogen and the hydrogen unites with hydroxylto form water.

Considering the process as applied to a paper recording sheet infacsimile recording, as will be further considered hereinbelow, when apoint on the paper is between the electrodes, positive elecrate becomesvery slow and alkaline couplingv accelerates, and usually all of thediazonium compound in the recorded area couples before the paper dries.In general, amino and hydroxy groups direct coupling under acid andalkaline conditions, respectively. Thus, it is possible for both acidand alkaline coupling to be manifested in a given reaction leading toazo dye formation.

Without intending to be restricted to any oi the theoreticalexplanations provided hereinabove or to any suggestions as to thecharacter of the reactions involved therein, or in the azo dye formationgenerally, it will be noted that aneX- planation in the form ofequations involvingthe production of diazonium salt electrolytically,and

the coupling of this salt, in accordance with the preferred inventionembodiments, is presented in U. S. Patent 2,306,471, referred to above.v As previously stated, the preferred procedure in accordance with thepresent invention comprises adapting the solution for facsimilerecording by electrolytically diazotizing an amine, in an alkalinesolution which contains an alkaline reacting coupling reagent.

The ingredients utilized in accordance with the invention, andespecially in its adaptation to facsimile recording, comprise thefollowing:

(a) An aromatic amine, desirably a primary amine.

(b) Anitrite.

V (c) Analkali.

' (d) A coupling compound.

(e) An electrolyte.

(f) Water or other solvent in which electrolytes ionize.

Concerning the amines required for producing the diazonium compound,substantially any diazotizable amino compound will sufiice. Mainlywithin the purview of such class of compounds are the primary aromaticamines, and especially where the latter are soluble in mildly alkalinesalt solution, and are not too readily oxidized electrolytically or byair oxidation.

Among the amines which may be utilized are monoamino benzene compounds,polyamino benzene compounds, amino-naphthalene compounds, aminopolyphenyl compounds, heterocyclic amines with a nuclear attachedprimary amino group such as the amino quinolines, amino pyridines andamino pyrimidines. The presence of a sulphonate group in such aminestends to enhance the stability of the background of the carrier towardslight although the dye may, in some cases, manifest somewhat lessfastness to washing. Typical illustrative sulphonates are the sulphonicacids of amino-benzene, -naphtha- 6 le'ne, or -diphenyl compounds andvarious amino naphthol sulphonic acids.

The following are illustrative lists of-amines and coupling compoundswhich may be utilized:

Ammas Monoamino benzene compounds Sodium formanilide Anilineomega-sulphonic acid 4-aminoacetophenone .4-aminoacetophenoneoximeAnthranilic acid 4-aminobenzoic acid 3-aminobenzoic acid Metanilic acidSulphanilic acid 2,5-dichlorosulphanilic acid Z-aminotoluene-B-sodiumsulphonate 4-aminotoluene-2-su1phonic acidOrthonitroanilineparasulphonic acid Paranitroanilineorthosulphonic acidParaaminobenzophenone f Paraaminobenzophenoneoxime Metaaminophenols-aminosalicyclic acid hydrochlorid Orthoaminophenolparasulphonic acid2-amino-4-chlorophenol-G-sulphonic acid Orthoaminodiphenylparasulphonicacid Acetoacetanilide oxime parasulphonic acid 2 l-metaaminophenyl-Ii-ca r b o x y -5 p y razolone 1 Hydroxylamine with No. 23 1Acetoacetanilide hydrazone parasulphonic acid Y Polyamino benzenecompounds -(1) All amino groups on the same benzene ring.

(2) At least two amino groups on difierent benzene rings.

. Benzidine Dianisidine V r Solubilized dianisidineBenzidinemonosulphonic acid Benzidine-2,2'-disulphonic acidBenzidine-3,3' -disulphonic acid Orthotolidine-2,2 or -6,6' -disulphonicacid 4,4-diaminobenzophenone 4,4-diaminobenzophenoneoxime4,4'-diaminostilbene-2,2'-disulphonic acid4,4:diaminodiphenylaminosulphonic acid.

See footnotes on following page. 7

Naphthalene compounds- Qrt'honaphchionic acid Sodiumna'phthionateLaurents acid Cleves 1.6 and 1.7acids Cleves 1.6 sulphonic acid Periacid" Disulpho S salt Kochs acid H 4-acetylamino- 1,7-Cleves acid Tobiasacid Dahls acid Broenners acid Amino F acid 66. Badische acid 67. AminoR acid Acid IV or C acid 69. 2-naphthylamine-5',7-disi lph'oni'c acid70. Amino G acid I 71. Naphthanil Red" 73. J acid 74. M acid '75. Gammaacid 76. S acid 1 I 7'7. Chicago'or 2S acid 1 78. Monosodium H salt 1'79. K acid .80.212 acid (oxyamino) 1 81. R" acid '(oxyaminm 1Heterocyclic compounds COUPLING COMPOUNDS Benzene" compounds ".2Resorcinol:

. 4-cl1lororesorcino1 Z-nitroresorcinol Salicylaldehyde Salicylaldoxime5:-chlorosalicylald'ehyde 5-chlorosalicylaldoximeOrthohydroxybenzalacetophenone OrothydroxybenzalacetophenoneoximResorcylaldehyde .Resorcylaldoxime Resorcylic acidParahydroxyacetophenone Parahydroxypropiophenone ResacetophenoneResacetophenoneoxime Phloroglucinol Metaaminophenol AcetoacetanilideIsonitroscacetoacetanilide- IsonitrosoacetoacetanilideoximeAcetoacetanilideoxime Acetoacetanilide hydrazone2-chloroacetoacetanilide 2-chloro-isonitrosoacetoacetanilide2,5-dichloroacetoacetanilide 4 109. 2,5-dichloro-isonitrosoacetanilide110. Acetoacetanilide-1oarasulphonic acid These chemicals may act bothas amines and as coupling compounds. Usually, when involved indiazotization and coupling reactions, some molecules of these compoundsact as amines, others as coupling compounds, and the remainder in bothcapacities, forming mixtures of azo dyes. Many of the other. amines,particularly in the naphthalene series, w1 ll act also ascouplingc0mpounds" if. no hydroxy coupling compounds are present.

'lhis acts as an amine, although it does not contain an ammo group. i

'. Beta naphthol 1,5-dihydr0xynaphthalene1,7-dihydroxynaphthalene-4-sulphonic acid Dioxy S acid Nigrotic acidYellow acid Red acid A acid Chromotropic salt or acid2,7-dihydroxynaphthalene Phenyl J acid Benzoyl J acid Di J acid urea Jacid imide J acid M acidv Gamma acid Phenyl gamma acid Chicago or 2Sacid Monosodium H salt Chloro H acid Phenyl H acid Acetyl I-I acid Kacid 2R acid (oxyamino) R acid (oxyamino) Acetoacetanilide oximeparasulphonic.v acid l-metaaminophenyl 3= carboxytirpyrazcloneHydroxylamine with No. L12 Acetoacetanilide hydrazone parasulphonic acidOrthophenylenediamine Metaphenylenediamine ParaphenylenediamineChloroparaphenylenediaminedihydiroc h 1- 0- ride2,5-diaminobenzenesulphonic acid dihydrochlorideDiacetoacetyl-parapheny1enediamine Diisonitrosodiacetoacetylparaphenylenediamine Diacetoacetyl paraphenylen'ediaminediox ime2,4-diaminotoluene 2,5-diaminoto1uenedihydrochloride2,4-diaminoanisoledihydrochloride 2,5-diaminoaniso1edihydrochlorideTriaminotoluenetrihydrochloride 4,4-dihydroxybenzophenone4,4-dihydroxybenzophenoneoxime Metadiethylaminophenol' Metadigallic acid(tannic acid) Naphthalene compounds Alpha naphthol Alphahydroxynaphthoic acid Schaeffers alphanaphtholsulphonic' salt Nevilleand Winthers acid L acid N-phenyl Peri acid RG acid I Andresens acidSchoellkopfs acid Oxy Koch acid Beta hydroxynaphthoic acid Naphthanil OASchaeifers acid F salt Bayers or Crocein salt Disodium R. salt DisodiumG salt Naphthoresorcinol Miscellaneous compounds 1'77.

DiisonitrosodiacetoacetylethylenediamineMonoisonitrosodiacetoacetylethyle n e d i a mineoximeMonoisonitrosodiacetoacetylethyl e n e di a minedioximeDiisonitrosodiacetoacetylethylenediami n e oximeDiisonitrosodiacetoacetylethylenediami n e dioxime Relative to theproportioning of the ingredients, as a general rule by way of estimateand not restriction, approximately 0.03 gram molecular weights (0.015for diamines) of amine and of a mono-valent nitrite per liter ofsolution produce quite satisfactory results. Usually 0.025 grammolecular weights or mols of amine are used per liter of solution forpaper that is treated at the recorder, that is, for paper which issubjected to the diazotizable solution substantially at the time thatthe recording is made.

A comparatively wide range of nitrites are available, the requisitebeing an ionizable compound, desirably a metallic nitrite. Whereas theexamples herein involve the use of sodium nitrite, it should be clearthat this compound is referred to merely as illustrative of a convenientmaterial which may be utilized in the diazotization procedure. Whilenitrite sodium provides entirely satisfactory results, the same may besaid of potassium nitrite as well as of many other metallic nitrites. Inview of the fact that neutral or alkaline solutions of sodium nitriteare comparatively stable, this reagent is particularly desirable inrecording solutions prepared for storage over a substantial period priorto usage.

It has been found that excess nitrite does not impair the backgroundpermanence of electrolytic diazotization recordings and is in factbeneficial because it causes a greater percentage of the amine to bediazotized, and consequently permits a decrease in the concentration ofamine with no loss in color intensity. Concentrations of 0.025 and 0.05gram molecular weights of amine and of nitrite, respectively, per 1000cc. of solution, usually give excellent results.

Similarly, a substantial latitude in choice of alkaline reagent isavailable, but for purposes of illustration herein, recourse is had tosodium The usual content of sodium hyhydroxide. droxide may becharacterized as that required to neutralize all strongly acid groups inthe amines and coupling compounds, and to provide a slight excess(usually 20 cc. of normal NaOH per liter or recording solution).

Where the alkalinity pertains to the recording solution and is notparticularly critical, simple expedients for its approximate evaluationare available in the form of the so-called Beckman l 10 instrument orother commercial devices. Similarly, a small piece of LaMotte Oleo Red BpH test paper may be immersed in the facsimile recording solution for afew seconds. The alkalinity is satisfactory if the paper turnsorangebrown, insuflicient if yellow or orange-yellow, and excessive ifred. It should be noted that insuflicient alkalinity is more harmfulthan excessive, since it impairs the background permanence; on the otherhand, a stronger signal in the form of electrical impulse is requiredfrom the amplifier, and half tones are impaired, when the solution isexcessively alkaline.

As a general matter, the color intensity at full electric currentdepends on the alkalinity and the amount of diazonium compound iormed.Ihe deepest color is usually formed at a pH of 7.5 to 9 which is notalkaline enough for good background permanence. At a pH of 6 to 7.5,hydroxy coupling is too slow in some cases, and prematurenon-electrolytic diazotization discolors the paper in others. At thecompromise pH range of 9 to 11.5, the color intensity is not sacrificedunduly in order to gain in background permanence.

The diazotizable composition and the treated carrier, such as paper, maybe stored a considerable period of time if thesolution ismodcratelystrongly alkaline. A pH range of 7.5 to 12.5 is applicable, althoughbest results are obtained Within the range of 10.0 and 11.5. As the pHdrops, the stability decreases, the tendency of the background to darkenon standing increases, and the sensitivity of the reaction increases.

In lieu of sodium hydroxide, other strong bases may be used, such aspotassium hydroxide, barium hydroxide, or-a quaternary ammonium.hydroxide. On a weight basis, the amount of alkali used may vary from0.01 to 0.12 gram molecular weights per liter of solution, dependingupon the original acidity or alkalinity of the other ingredients, and isadjusted to the predetermined pH of the finished solution, which, asabove suggested, may desirably be within the range of 10.0 to 11.5.

The coupling compounds are desirably soluble in a mildly alkaline saltsolution and preferably subject to the same oxidation limitationsasdiscussed above in connection with the amines. Aromatic compounds withhydroxy, amino or active methylene groups, ortho or para, tounsubstituted positions in the ring will usually couple. sulphonicgroups have the same effect as in amines. Resorcinol, phloroglucinol,the naphthols and their sulphonic acids, 8-hydroxy quinoline, and someamino naphthol sulphonic acids have given good results. Some aminonaphthol sulphonic acids (for example, gamma, H, J, S and 2S acids) mayeither diazotize or couple. Good recordings may thus be obtained, usingthe same chemical for both diazotization and coupling. However, mostamino naphthol sulphonic acids give recordings that require washing inorder to prevent the backgrounds from darkening during storage.

Chromotropic salt is considered the best allround coupling compound,giving darker colors than any of the others having reasonably permanentwhite backgrounds. The aceto-acetylamino compounds, their oximes andhydrazones, and the isoxazolones and pyrazolones derived from them, giveyellow or orange colors, the oximes and hydrazones being most effective.When added to facsimile recording solutions conexample hereinbelow.

The amount of coupling compound utilized may vary between 0.01 to 0.02gram molecular weights, although 'more'may be utilized without harm.Usually approximately 0.015 gram molecularweights of coupling compoundper liter of solution provides excellent results, and a greater amountrarely shows any-improvement in recorded color intensity.

As above indicated, the coupling compound may be-o'f the type whichreactsjin alkalinema dium or in acid medium, although the "former ispreferable. It is'interesting to note that some amino compounds mayfunction as coupling agents regardless of the pI-I, and manydiazotizable primary amines serve-in'the dual function of amine andcoupling compound. Underalkaline conditions, the hydroxy-coupling rateof reaction is generally so much greater than the amino coupling ratethat substantially little or no amino coupling takes place in alkalinesolution when both amino and hydroxygroups are present.

As for the electrolyte, NaCl is quite satisfactory, but there is nointent to be limited to the use of this salt. Other strong neutralelectrolytes such as NaBr, KiBr, KCl, LiCl, BaClz, CaClz, MgClz, K2304,Na2SO4, MgSO4, etc., "may besubstituted for sodium chloride. Some dyeintermediates are more soluble in potassiumchloride solutions, in whichcases the substitution is made. Lithiumzchloride has been found toretard the time of paper drying, but .the same result is cheaper andmore effectively obtained by 'the'use of wetting agents. An additionalelectrolyte'which has provided excellent recordings, while at the sametime obviating the corrosive efiect of nascent chlorine, is sodiumsulphamate,

naosomnz The amount of electrolyte required is not critical. Lowconcentrations require more electric current, while excessively highconcentrations may cause partial precipitation of the dyeintermediates;About two-thirds of a -mol (a mol equals one gram molecular weight) oftotal electrolyte per liter of solution is fully adequate. Forconvenience in making the sodium ion correction to the Beckman pH meterreadings, a total sodium ion concentration of 0.64. mol is used. Thetotal 'sodiumpresent in all the other ingredients is subtracted from0.64,-.theremainder representing the amount of sodium chloride to beadded.

"Where NaCl is utilized, itfhas been-found'that the totalconcentration'of s'odiumions equal to 1.0 gram molecular weightperzliter istquite effective, although good recordings have beenobtained in some cases withaslow as 0.1 1andashigh'as 3.0 gram molecularweights of sodium'per'liter.

Substitution of sodium oxalate f'or'part of the sodium chloride retards=thebackground darkening of damp pretreated papenalthough the elec- 1 2tric current requirements areincreased, and t e halftone response issomewhat'impaired. Oxalates have little effect on the backgroundpermanence of recordings exposed .to light -.after drying, and their useis advisable .primarily with damp treated paper.

It is, of course, apparent that water functions as a very desirable andeffective solvent within which the diazotization and azo dye formationare carried out. However, various non-aqueous neutral solvents that.permitelectrolyt-es toionize may be substituted forall or a part of thewater. If approximately half the water is replaced by alcohols orglycols, the freezing point-of :thersolution is lowered to such anextentthat recorders may be operated outdoors in winter.

Ethyl, methyl and isopropyl alcohols evaporate more rapidly than water,so that the paperidries too quickly in summer but in winter the addedspeed is desirable. Normal propyl alcoholdries at approximately the samerate as water, and may be used both summer and winter. The tendency ofthe propanol-water-saltmixture to separate into two liquid phasesis-eliminatedby replacing ten per cent of the propanol with ethyleneglycol. Larger amounts of the .glycols are unsatisfactory, as their lowvolatility causes the recordings to be permanently limp andmoist.

Some solvents, notably Cellos'olve,methylicellosolve, andmost denaturedethyl alcohols, gradually react with'the alkali in the recordingsolution, which eventually becomes acid (unless more alkali isoccasionally added), whereupon diazotization and coupling begin, causingpaper treated with the solution to become discolored. jNormal propylalcohol and ethylene glycol do not reduce the alkalinity.

It will be noted that auxiliary chemicalsare of substantial usage, andcontribute materially to the control of the diazotization, dyeformation, and recording generally. .Such substances as oxalates,antifreeze solvents, hydroxylamine and hydrazine maybe considered eitheras auxiliary chemicals or as replacements for ,part of the essentialchemicals.

An important role may be attachedlto theuse of auxiliary chemicals inconnection withthedye formation, and particularly where facsimilerecording is .concerned. These substances contribute materiallyto thecontrol of .the diazotization, dye formation, and recording generally.

Urea, thiouera, and, .toa'still greater extent, dicyandiamidinehave beenfound to improvelthe color intensity. About 1 ml mols of either-of thesecompounds per .mol of amine are used. Thiseifect is more apparentwhencombined with that .due to excess nitrite. .If .a sulphate -.orhydrochloride of these bases is used, sufficient caustic soda or otheralkali :must be added to liberate the free base, in ordertomaintain'theproper pH range.

Wettingagents maybe utilized in the treatment of the carrier, such aspaper. :Many of such wetting agents and their general ifield'of usage aswell as chemical characteristics arerset .forth in the Journal ofIndustrial and Engineering Chemistrywolume 31,J.une-1939, pages-6439.

Wetting agents which have been found :quite effective aresulfonatedether (see pageo9, vol

ume 31 of Journal of Industrial andsEngineerin'g Chemistry,.January,1939) as well :asthe sodium salts of aryl'alkyl'poly ether .sulfonate"(p 130, volume .35, J ournal of Industrial. and Engineering Chemistry)and 'dioctyl ester sodium sulfosu'c- 13 ci-nic acid (page 126, volume35, Journal of Industrial and Engineering Chemistry).

The rate of penetration of the dye forming solution into the carrier orsupporting material, such as paper, is most rapid, at high alkalinityand low surface tension of the solution, as well as at high atmospherichumidity. It is in this connection that wetting agents have been foundhighly efiective in reducing the surface tension sufiiciently foradequate wetting to occur in a brief interval of paper submersion time,desirably approximately six seconds, regardless of the humidity andalkalinity prevailing. As an ex-. ample of the quantity of wettingagent, 0.8 of wetting agent solids per liter of solution has been foundto aiford adequate wetting when the paper is immersed. Where the paperis supplied with the dye forming solution by contacting only one side ofthe paper with a wet roller approximately 1.5 grams of wetting agent perliterof solution may be essential.

The desirability of resorting to wetting agents in the recordingsolutions is emphasized by the fact that without the same it has beennecessary to .submerge the paper for at least two minutes to insureadequate wetting on dry days. The use of pretreated paper, i. e., papertreated with recording solution prior to its utilization in therecording apparatus, has heretofore proven impractical for theelectrolytic treatment when subjected to moistening by water in theabsence of a wetting agent. Differenttly stated, the wetting agentcauses the water to penetrate pretreated paper more rapidlythan thesolution penetrates untreated paper. Moreover, an additional function ofthe wetting agent is to cause the recording solution on the surface ofthe paper to continue penetration until saturation occurs, where excessliquid is available on the paper surface. Any remaining excess Olfliquid is removed by any conventional expedient, such as by a doctorblade or a preheater.

An undue amount of liquid on the paper may function to cause blurring atthe instant of printing. Where the interval between paper wetting andfacsimile printing is comparatively long, the tendency is for the paperto become partially dry, causing streaking and paper scufiing when theprinting is applied. The wetting agents serve to retard the rate ofdrying at this stage of the operation.

Glycols and other high boiling solvents also retard drying at roomtemperature andimprove wetting, but they are not as eifective as wettingagents, thereby necessitating much greater concentrations. If the damppaper, after being subjected to recording, is passed overa hot rollerfor the purpose of drying and ironing it, the glycols require a greaterextent of heating, since at higher temperatures they are more efiectivethan wetting agents as drying retardants. Wetting agents similarly areadvantageous in the case of pretreated damp paper which is stored in amoisture-proof container, to be later positioned in a slotted containerat the point of unrolling at the recorder.

An element which materially affects color intensity is, the amount ofdiazonium compound formed electrolytically. It will be appreciated,

"in this respect, that the halftones of photographs except at very lowcurrents where the color intensity drops sharply due to theso-called'threshold value effect. In view thereof, reducing agents aswell as high alkalinity serve to detract from the light tones. Thisthreshold eiiect maybe compensated for by resort to color-deepeningchemicals, illustrated by urea, thiourea, and dicyandiamidine, whichimprove the halftone characteristics by accentuating the light tones.

Other substances which tend to deepen the color or improve backgroundpermanency are barium and calcium chlorides which may be substituted inpart, or'entirely, for sodium chloride as the electrolyte. Suchsubstitution may, however, not bewithout its shortcomings in view of thepossibility that the solubility of the dye chemicals may be lowered andon occasion objectionable sludges may be cformed.

extent of diazonium compound formation, and

Through the choice of primary amines and coupling compounds used agreatvariety of colors may be'obtained, although orange, red and purpleshades predominate. ,In general, the orange dyes give recordings whosebackgrounds are more permanent without washing than the reds, purples orblues. Furthermore. it has been found that alpha-naphthalene compoundsgenerally give darker colors, but with less permanent backgrounds, thanthe corresponding beta compounds.

On the question of background permanence. some amines and couplingcompounds, in some cases those having two or more amino or hydroxygroups onthe same benzene or naphthalene ring, may manifest anunduetendency to air oxida tion and it may be desirable as a generalexpedient to wash recordings made through the use of such reagentswithina few hours after such recordings in order to prevent excessivebackground darkening. on storage. Taken as a whole, the remaining aminesand coupling compounds .give satisfactory recordings which retain theirwhite backgrounds, or at least do not darken suificiently to impairtheir legibility and utility when stored several years in a fillelorholder.

' As previously suggested, various chemicals function to retardbackground'darkening, among which are glycols. These substances are usedin the proportion of approximately 100., cc. per liter of solution. Insome cases, they reduce darkening due to the slow reaction duringstorage, but are not as effective with respect to darkening whichresults fromlight exposure. V

Reducing agents, such as sodium hydrosulphite (Na2S2O4-2H2Ol andacetaldehyde sodium bisulphite (NaOSOz-CHOHCE) tend to retard thedarkening action of light, but may not pre clude slow darkening.Quantities varying from 0.002 to 0.01 mol per liter have been utilizedwith effective results within the scope indicated. The reducing agentsspecified are merely illus trative, since other reducing agents have asimilar efiectp Such other reagents are tartrates, formates, sulphites,thiosulphites, other hydrosulphites than sodium, mentioned above, etc.

The effect of alkalinity upon background darkening has already beenrecited, and the same applies to the optimum range of pH between 9.5 and11.0, especially where sodium chloride is used as the electrolyte.Higher pH may cause weakeningand decomposition of the paper, while lowerpH may result in partial oxidation and partial self-'diazotization ofthe amines. The pH of the paper before treatment with the solution isknown to effect the final alkalinity of-the treated paer; therefore, ifan acid paper is used, the alkalinity of the solution should beincreased to com.- pensate therefor. 7

Complex cyanides of iron, chromium, or other metals, in some instancesimprove the iastness of thedye records to Washing and deepen the shade,or even alter the dye color. Noteworthy is the fact that the dyes are onthe whole distinctly faster to washing than the intermediates from whichthey are formed. As a result of this, washing may be resorted to forremoving unused chemicals from the unrecorded areas, thereby leavingintact the dyes corresponding to the subject of transmittal. As ageneral rule, recordings intended to be washed should preferably be madeat a pH range of 8.0 to 10.0 within the broader range of -9 to 11.5; inthis way advantage is taken of the greater color strength and increasedfastness during such pH range. Urea, thiourea, and dicyandiamidineincrease the fastness to washing. Thus these compounds serve thedualfunction of improving color strength as well as color fastness.

The minimum current which is required to produce a faint-color isreferred to as the threshold value. Before diazotization can take place,the initial alkalinity of the wet paper must be overcome. If reducingagents are present they are oxidized by part of the current, leavingless foracidi-ficationand diazotization. Thus the reducing agentsreferred to hereinabove show this threshold value efiect. With neutralsolutions or in the absence-of reducing agents, small stray currentscause streaks and spots of color on unrecorded areas, thereby detractingfrom the appearance of the recordings and in some cases seriouslyinterfering with the legibility of the small type.

The application of a constant negative potential to the printingmechanism has an eiiect anal- .Ogous to that of high alkalinity inpreventing streaks due to stray currents, since the positive facsimilesignals must overcome this negative voltage before color appears. Thisexpedient is, however, not without some difficulties in the way of anincreased rate of corrosion of the negative electrode, and in the caseof certain metals produces a pale negative recording on the back of thepaper. It may also tend to eliminate the lighter shades in reproductionof photographs.

Illustrative of desirable embodiments of the invention, the followingexamples are presented:

Example 1 1 Mols per .Gramsper Name and Liter 250 Liters FEE-MIXEDINGREDIENTS B enz,idin e-3-3-.disulphouic Acid (amine) .015 1634. 5Aetoacetanilide (coupler). 002 .88. 5 ,Schaeifers Salt (couplcr).. .003231.0 Ohromotropic Salt (coupler)- .010 I 1248.7 Sodium Hydrosnlphite(auxil .003 157..5 Urea (auxiliary) .010 150. 2 Sodium Chloride(electrolyte) .450 6576. 1

SEPARATE MIXTURE Sodium Hydroxide (alkali) .061 620 or 6.10 1 ms.:SodiumJNitritc (nitrite) 060 l0-l3 .=.2 ,or 3:00

I ers. Sodium salt of aryl alkyl polycther .08% 750cc. suliouate(wettingogentlt Example 2 Mols per Grams per Name Liter Liter PRE-MIXE-DINGREDIENTS Benzidine is disulphonlc Acid 015 .6. 538 Chrometropw Salt.015 6. 000 Barbituric Acid 004 .0. 512 Sodium Hydrosulphite 0028 0. 588Dicyandiamidine' Sulphate 0010 0. 316 Thionrea 0010 0. 070 SodiumCarbonata 030 3. 721 Sodium Chloride .300 17. 536

SEPARATE MIXTURE Sodium Hydroxide, 2.5 Normal. .050 20.0 00 SodiumNitrite, 5.0 Molal .074 14. 8 cc It will be noted in the above examplesthat while the ingredients in each instance are separated into twogroups, this is primarily indicative of a desirable expedient forpackaging or storing the reagents prior to usage. However, consideringthe compositions from the standpoint of their substantive content, theycomprise the reagents specified in both groups.

As illustrative of the preparation of the compo sition of Example 1, theproper amounts of .each of the pre-mixed ingredients are weighed, andall are thoroughly mixed mechanically. A conveni, ent method utilizes aninclined rotating drum containing pebbles or metal balls tobreak upanylumps in the chemicals. The mixture may be stored in bulk or packed insmall packages each containing the required quantity.

Since measuring liquids is much more convenient than weighing solids, itis advisable to use concentrated stock solutions of sodium hydroxide andsodium nitrite instead of the corresponding solids. Approximately 2.5normal sodium hydroxide (102 grams per liter) and 5.0 normal sodiumnitrite (345 grams per liter) are adequate. The wetting agent is alreadyin liquid form.

The composition adapted for electrolytic .diazotizing and coupling isprepared by dissolving the pre-m-ixed chemicals and sodium hydroxide inapproximately three-fourths the required water, adding sodium nitriteand the remaining water, and filtering or decanting to remove sediment.The wetting agent may be added at any time during or after thepreparation, and varies in amount with operating conditions, although itis not critical.

The following table is indicative of expedient amounts of each componentutilizable in a recording solution, based upon the two different unitvolumes, namely, the quart and the liter:

Pro-mixed Sodium Sodium Total Volume of Ingredlents Hydroxide NitriteRecording Solution (2.50 Normal) (5.0 Normal) grams cc.

'1 quart 38.181 32.50 23.091 11.356 1 liter 40. 346 34. 34 24. 40012.000

wow

v 13 propriate proportion. A desirable pH for the The solution isprepared' similarly to Example mp n W n th p ive portions have 3, exceptthat it is clear' and does not require been admixed 15 between 10-75 andfiltration. The same recording procedure gives Additional examples areas follows: orange-Brown'recordings on a white background, Example 3 5 Ywhich turn pale yellow on exposure to light, and

INGREDIENTS Amount used No. Name Chemical Formula Use per liter oisolution I Orthotolidlne 22' disulphonic l0l d.-- I 8011i CH; Amine..V-.I 5.054 grams.

II Ohromotroplc Salt 0H 0H Coupling Compound 3.640 grams.

more 7 more To dissolve (I) and make the 52 co.

III Sodium Hydroxide (Normal solution)-.-

solution alkaline.

IV Sodium Nitrite (twloe normal solution). To dluotize (I).. 15 on.

V Sodium Chloride (Common sal Elgctrolyte to permit current to 52.5grams.

,ow. r To totalrvol me ol1000 on.

VI Water In the preparation or th ev s olution, (1), (11behayelikelExample 3 recordings when washed. (III) and (V) are dissolvedinalgout 800 cc. water. The dye is amono azo dyeaus follows. Since thecommercial product (I) contains am- 1 monia and some insoluble matter,the solution is HO OH filtered, and (1V) and the remaining water are 85then added. x a t 1 The formula of the dis-.azodye formed is as V Afollows: 1 H

011 on on, f 50.1! V t on on our Hi Hols SOaH r Hols son! Example 4 I Vmu my I Amountused No. Name Chemical Formula l Use ,per liter oisolution 1 Sodium Naphthionateune N'rr, mama.-.".-.;-,Q;,.;-,7.3l52grams.

om; a I I l H Phl luoinol COB Com nd. 1.260 nms.

orog no on D P0 7B1 111 SodiumHydroxlde (normal solution).... mom..-a,some.mid ummer 4000. IV Sodium Nitrite (twioonormalsolutlon)...NBNO)--. Todiozotize m 15m. V Sodium Chloride NnCl Electrolyte topermiteurrent to flow 58.5 grams. VI Water 'HQO To total volume oi 1000cc, 3 i

ga ta-52c 7 Em t? I .L j "if'r'zii' IINGREDIENTS 2*- Amountused No. NameChemical Formula Use per liter of solution I 4-Acetylamino-1-7-ClevesAcid NH: Amine 9.228 grams.

. Hos

V NHCOCH:

II Gamma Acid on Coupling com oundandiimiiiewhll;-2390 m.

L I i OaS III Sodium Hydroxide (Normal so111tion).-. NaOH .i To dissolve(I) and (II) and make the 70 cc.

. solution alkaline. IV Sodium Nitrite (twice normal solution).-. NaNOzSame as Example3 cc.

V Sodium Chloride (common salt) NaCldo I i 25.6 grams. VI Water H2O 'Iototal volume of 1000 cc.

hea m nis r md ii .fiiisainrles 3' n 2 ears were i'eh fi f h' 4,filtration being unnecessary. Excellent dark purplish-brownrecordings'on a white background are obtained. On standing, even in thedark, the background gradually becomes pale purple,

' are employed to'facilitate 'quick'penetration of "'"the solution; fromofito lzdgrams"of-wetting agentsolids per "liter' of recording solutionis usually sufiicient for this purpose. Among the but if the freshlymade recording is washed with eifects produced are more rapid solutionpenewatertl'ie' background darkensmuch-more slowly and to a far lesserextent than that of unwashed recordings. The dyeis a=-:mixture, butconsists mostly of the following: R

NHCOCH: NH:

Irrespective of the predetermined coloration] to be obtained, dependentupon the reagents util-* ized, the supporting material, such as thepaper, after having been appropriately treated with the,

tratfion"-i'nte paper and slower drying after bine with the amine beforediazotization weakens the recorded color. If a sulphite with a fairly .1*high initial ,wetstrengthds used, aymoderate "treatment-gives adequatestrength ,w'ithout ex- 5 cessive cOI rryVeakeningM-The treatment ispref- ,erabln-iannlied to the unsized pap,er.'.

reagents, is passed through the facsimile recorder Effective results maybe obtained by combinin Wet or moist condition. A desirable facsimilerecorder which may be utilized is the bar-helix type, the bar servicingas the anode and the helix ing formaldehyde and urea with the recordingsolution which has been freshly prepared, glycols being includedtostabilize the initial resins wneeareatedwith- "urea-formalde hyderesins, sulphite paper increases in wetstrength td -the- 'pointwhereitbecomes usable, although the tendency of formaldehyde to com-Tproviding the cathode. However, it is apparent forgned. However, suchsolutions are not parthat the performance of the recording is not re '50't c ilarly stable when retained in storage for sevstricted to the-"useof anyparticulartype of ap- --era1--ci y inoe a-s tml prop i n of thparatus. V v amine content is consumed, thereby resulting uilng pbn tactith th printing el ctrod of -in-a -decrease in recordedcolor-"intensity. Freshthe.recorder,.the.diazoniumcompoundisformed, ,J11 78 1??? Qd. EQ HH HS .QifillE WP? l fi l hi 19b. hchcoupleswith.thacornlieeromreneot b fiawtaining dry Dre-treated r a ewhich has cut. Desirably, the treated or sensitized paper is fedcontinuously from a roll. Where the paper has not been sensitized, it isinitially fed from the roll through the appropriate immersion :bath

'been't reated withthe reagent solution and dried preliminary to itsutilization as a recording sheet) may set the resin, and the dry storagecondifitions ,serve to prevent or minimize the relafor impregnation withth dye i t di t d tively' slow chemical reaction between theformalauxiliary compounds, the excess immersion solution removed, andthepaper pass'ed direotly to the recorder. 3

The reference'to paper as the supporting matedehyde resin and the amine.

=A fter subjecting thesheet to electrolytic trea menu-especially wherefacsimile recording is inyolved, the carrier in a dry state is desirablykept "rial or carrier has been recited solely by way of in t folderProtected from posure to light.

illustration Substantially any fibrous material capable of being dyed byan 9.20 compound is within contemplation; including materials el ulosici as fabric}. 6.10m;ana-maea types daylight? IT. with? 93 1e;-Washing' the freshly recorded sheets, regenerated or otherwise. Quitedesirable- "sheets thoroughly twithnwatermat the most only results havebeenobtainecl-withan all-rag-sheet;--

surface-sized with glue-formaldehyde in order to impart adequate wetstrength. Similarly, good results have been obtained with partiallyparchmentized wood pulp paper. In the case of paslightly-weakens theeoloringof thedye which has been formed; at the same time, such washingsubstantially improves the permanence of the background.

Under preferred conditions of operation, the re- A 21 i cording paper,after having passed through the facsimile receiver may be subjected to afixing bath for the purpose of rendering the dye more permanentin-nature and/or to aid in the preservation of the white or neutralcharacteristic of the background. The paper is then desirably washed, asabove indicated, to remove any chemicals which remain in theundiazotized portions of the paper in "order to thereby minimize anytendency toward gradual fading of the color pro-. duced or darkenin ofthe background when. the recorded copy .is exposed to light and/or air.

In preparing the various reagent solutions for utilization to saturateor impregnate thesupporting material, certain precautions and details ofprocedure may be advisible, dependent upon the particular circumstancesinvolved. Thus, where all the ingredients of a. solution are neutral oralkaline upon their being dissolved in water, they may all be dissolvedtogether. The sodium and potassium salts of aminoor hydroxy-naphthalenesulphonic acids fall in this class. Where the amines, couplingcompounds, or other ingredients are free acids as distinguished fromsodium or potassium salts, it is necessary to omit the sodium nitritefrom the solution until all the acidic compounds have been dissolved bythe excess alkali required to give the proper final alkalinity. Failureto observe this precaution results in the formation of diazoniumcompounds in the acidic zone adjacent to each dissolving crystal oftheacidic compounds, with subsequent coupling and dye formation when thediazonium compound hasreached the alkaline w zone. Such solutionsdiscolor any paper that is treated with them.

On storage, the solutions may tend to darken because of auto-oxidationof some of the ingredients, especially if exposed tolight in clearbottles and to air in partly emptied bottles; sometimes this' oxidationcauses the formation of sediment, even though the solution wasoriginally filtered. Nevertheless, good recordings have been obtainedwith some year-old solutions, at a slight sacrifice 'in backgroundpermanence. Solutions that have become dark on standing may be restoredto their original color (amber, clear brown, or red) by the addition ofsmall amounts of sodium hydrosulphite.

Where the reagents areretained in their'solid form, all or part of themmay be packed in glass bottles, waterprooffiber or tin cans, or anyother suitable containers, so that the user merely dissolves thecontents of one or two containers in water, mixes the two solutions iftwo containers are needed, and adds more water until the required volumeof solution is reached. In those cases where impurities in' the water orin the chemicals cause sedimentto for the solution may either. befiltered, or allowed to stand several hours to permit the precipitate tosettle, so that the clear'liquid may be decanted.

' By separating the rest of the ingredients (in the containers for. drysolids) by layers of salt (which constitutes the greater part of thevolume of dry ingredients), any tendency for slow chemical reactionsbetween the ingredients during dry storage is avoided, since salt isinert with results, and avoids the necessity for thawing the ternativeprocedures are available. These may be listed as involving the followingthree methods: (a') chemical treatment of paper at the recorder, (b)damp pre-treated paper requiring no treatment at the recorder, and (0)dry pre-treat ed paper requiring treatment with water at the recorder.

Considering the recorder-treated paper, the untreated paper is fedthrough an immersion bath or over wet rollers, where it becomessaturated with a solution of the recording chemicals. After removal ofexcess solution by doctor blades, and of excess moisture, by naturalevaporation or by a heated roller, the wet paper passesthrough thefacsimile recording mechanism. This method is more convenientexperimentally, since both recording and paper treatment are combined inone operation. It has the advantage of lower cost for chemicals andpaper due to elimination of pre-treating costs, and is excellent for usein commercial high speed recording where properly instructed operatorsgive the recorders frequent attention. It may not be entirely suitablefor home reception of facsimile broadcasting, since it involves thehandling in the home of chemicals which require an element of care andprecaution to avoid spilling, discoloring of furniture and clothes. 7

With respect to the damp pre-treated paper (b) ,the treating andrecording operation may be separated, the paper being treated andrewound while still wet, and delivered in sealed moistureproofcontainers to the recorders. When required for use, the wet roll ofpaper is transferred to a slotted container in a recorder, from which itis fed to the printing mechanism. This method imposes less strain on thepaper than any other wet electrolytic recording method, as the damppaper does not stretch or wrinkle between the slot and the printingpoint. Consequently much weaker paper may be used. Quick starting withintermittent operation, a desirable feature in telegraph offices, iseasily accomplished by manually pulling out the paper for a distanceequal to that between the container slot and the printing point. Theinclusion of wetting agents in the treating solution eliminatesexcessive drying of the paper between the container slot and theprinting point during normal operation.

The shelf life of damp treated paper varies with the chemicals used andwith the alkalinity.

Usually, the interval within which it should be utilized extends forslightly less than three months from the time that the paper has beenprepared. Refrigeration, even with Dry Ice, does not harm either thechemicals or the paper and desirably functions to increase the shelflife. A temperature just above the freezing point of water has shownindications of providing the .best

paper before use.

Both metal foilwrappers and tin cans with or without internal coatinghave been utilized for packaging damp pretreated paper. In the case ofthe cans, a tendency toward rusting is manifested, and for this reasonthe metal foil is preferable. Tinfoil gives better results than eitherlead or aluminum foil, but it is believed that the moisture retentionmay not be as effective as in'the case of a sealed metal can. Theacidity of asphalt-laminated paper causes discoloration of the outerlayers of the pre-treated paper. Preferred results may be obtainable byuse of a metal foil wrapper on the treated roll of paper, together witha waxed fiber can, desirably with a screw top that is waxed after beingclosed.

In accordance with the above description, it

25 that they should be of the type which enter into the'compositions ofthe" dyes formed during electrolytic diazotization. Among thecontactelectrodes which havebeen utilized are stainlesssteel, tungsten,molybdenum, platinum, and platinumiridium. .In' general, the hard, inertmetals such as platinu'm iridium and the stellites provide the bestresults as recordinganodes. Non -magnetic stainless steels similarlygive good results, but the colors differ from that produced by theplatinum or stellite, and maybe less attractive in appearance, possiblyattributable to collateral reactions involvingthe iron. Ordinary: steelswhich are strongly attracted by magnets-do not permit any diazotizationreaction, but, onoccasionJthey' produce a moderatelypale greenrecordingwhich is believed to result from oxidation of the inter mediates. In thecase of 1 alloy electrodes, the percentage of azo color resulting fromdiazotization appears to increase asthe-magnetic characteristics of thealloy decrease. By way of explanation as a plausible hypothesis, it maybe that the magnetic metals create a strong magnetic field when thecurrent passes, and this magnetic lfield orients the electricallycharged ions in such-direce tions and in such mannerthat they preclude'the possibility of diazotization.

Copper alloys and electrodes generally made from copper or nickel tendto inhibit electrolytic diazotization recording and are, therefore, as ageneral matter not satisfactory for use as recording anodes, althoughthey give excellent results as cathodes. In this category is theberylliumcopper alloy.

Tungsten generally provides satisfactory recordings, but it manifests atendency. to build up a non-conductive coating, thereby requiring moresignal current for eifective recording as well as the occasionalnecessity for reversing the current during a brief interval in order toremove the coating.

The tendency is for the cathode to indicate substantially lesselectrolytic wear than the anode, since it is attacked only by nascenthydrogen and by increased alkalinity at the time of current flow; With abar-helix type of recorder, the cathode is desirably in wire form, andthe principal wear is due to abrasion which gradually renders the wireflat. The beryllium-copper cathode necessitates more frequentreplacement than the anode when the latter is either platinum-iridium orstellite. A cathode helix wire of stellite may outlast several stelliteor platinum-iridium anode printer bars.

It will be apparent from the foregoing that the use of compositionswithin the scope of the present disclosure enables the production ofdyes and pigments by subjecting solutions or mixtures of chemicals toelectric current. Such dyes or pigments may be obtained in the form of apaste, powder, or as a liquid solution, and subsequently adapted for useas coloring paints, inks, etc., or for dyeing various materials. It iswithin the contemplation of the invention to produce such dyes orpigments by intermittent or continuous reaction. Materials such asclothing, piece goods, yarn, paper, and generally any fibrous materialsusceptible to dyes, and particularly azo dyes, fall within the purviewof the present disclosure. They may be treated by immersion in acontainer filled with a solution of predetermined ingredients andsubsequently subjecting such solution to the flow of an electric currentin order that the dye may be fixed in or on the materials immersedtherein; thus, the dye application may be. in. 1211.6

26 formroi'; alsurface' coating or a' dyeingiwithi'n ithe fibrousstructure. Definitely contemplated isthe formationofthe' dye insitu." II While I have-described my invention in accord=ance"with-preferredembodiments"as to compositions, articles ofmanufacture, and procedure; .it is apparent that many variations andmodifications 'bothf as lt'o procedural details, compositions of matter,and 'articlesof manufacturamay b'e made without departing from the scopeofequivalents withinthe purview and spirit of the in- {Us I The term"facsimile" as used herein is intended to involve not only thereproduction on the re cording material. of a pre-existing subject, forexample a photograph which is scanned and reproduced in accordance with.the impulses em-' fanatin'g [from the scanning operation; but alsoembraces the recording of subject matter the process: of creationorformation without a 'Jphys- 'icallypre-existing subject. As illustrativeof this latter oategory wouldbe the recording of simply 'rnentalpreconception, for example a' pattern orfdesign; either of a singlecolorand 'fshades jthereoffor 'multicolors, which is Erecorded in accordancewith an: appropriate manual or automatic variation of the electricimpulses delivered ito' thelectrodes. Similarly in'zthis categoryJ isintndd"the recordingof an arbitrary or haphazard design, pattern orother subject, for example one secured by haphazardly or arbitrarilyvarying electric impulses delivered to the electrode by punching keys ona master keyboard having suitable electrical connections, by manually orautomatically varying resistance, or the like.

Having thus described the invention, what is claimed as new and desiredto be secured by Letters Patent is:

1. A fibrous sheet material for the electrolytic formation of an azodyestuif thereon having the surface thereof uniformly treated with anaqueous solution of a dyestuff forming composition consistingsubstantially of a diazotizable primary amine, a suflicient quantity ofan alkali metal nitrite to produce the nitrite ions necessary fordiazotization of said amine under the influence oi the electrolyzingcurrent, a water soluble neutral inorganic salt in addition to saidnitrite as the electrolyte in an amount to insure passage of theelectrolyzing current, a suflicient quantity of an azo dye couplingcomponent to couple with the diazonium compound when formed to producean azo dye, and a quantity of alkali surficient to impart to saidcomposition a pH on the alkaline side to therebypreclude diazonium saltformation until the fibrous sheet material is subjected to the action ofthe electrolyzing current said fibrous sheet material being free fromany azo dyestufi.

2. The article as defined in claim 1 in which the solution has a pHranging from 9 to 11.5.

3. The article as defined in claim 1 in which the diazotizable amine isan aromatic polyamine.

4. The article as defined in claim 1 in which the composition contains awetting agent to facilitate application of the composition to thefibrous sheet material.

5. The article as defined in claim 1 in which the composition contains acompound to improve the color intensity of the azo dyes, said compoundbeing selected from the class consisting of urea, thiourea anddicyandiamidine.

6. The article as defined in claim 1 in which the ionizable nitrite issodium nitrite, the elec-

